CLAS physics database search results Measurement E151M2341 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 114 -0.7402 0.8707 0.0615 0.75 222 0.3104 0.9785 0.0375 0.85 66 -0.7951 0.9241 0.065 0.85 234 -0.0217 0.9515 0.03 0.85 246 1.7362 0.7424 0.1294 0.85 258 1.0393 0.8181 0.0811 0.85 270 2.6277 2.6277 0.1929 0.95 246 -0.4479 0.8794 0.0442 0.95 258 0.7705 0.8747 0.0634 0.95 270 0.7057 0.8519 0.0593 0.95 282 -0.2234 0.7894 0.0341